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New scheme for finding candidates. Speed up sync. Improved SNR calibration.

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This commit is contained in:
Steve Franke 2019-02-02 16:29:17 -06:00
parent 40fd3f6551
commit 91e3dbdf20
3 changed files with 38 additions and 20 deletions
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15
lib/ft4/ft4_decode.f90
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@ -78,7 +78,7 @@ subroutine ft4_decode(cdatetime0,tbuf,nfa,nfb,nfqso,iwave,ndecodes,mycall, &
ndecodes=0 ndecodes=0
do icand=1,ncand do icand=1,ncand
f0=candidate(1,icand) f0=candidate(1,icand)
xsnr=10*log10(candidate(3,icand))-18.0 snr=candidate(3,icand)-1.0
if( f0.le.375.0 .or. f0.ge.(5000.0-375.0) ) cycle if( f0.le.375.0 .or. f0.ge.(5000.0-375.0) ) cycle
call clockit('ft4_down',0) call clockit('ft4_down',0)
call ft4_downsample(iwave,f0,cd2) !Downsample from 512 to 32 Sa/Symbol call ft4_downsample(iwave,f0,cd2) !Downsample from 512 to 32 Sa/Symbol
@ -89,15 +89,15 @@ subroutine ft4_decode(cdatetime0,tbuf,nfa,nfb,nfqso,iwave,ndecodes,mycall, &
! Sample rate is now 12000/16 = 750 samples/second ! Sample rate is now 12000/16 = 750 samples/second
do isync=1,2 do isync=1,2
if(isync.eq.1) then if(isync.eq.1) then
idfmin=-50 idfmin=-12
idfmax=50 idfmax=12
idfstp=3 idfstp=3
ibmin=0 ibmin=0
ibmax=374 ibmax=374
ibstp=4 ibstp=4
else else
idfmin=idfbest-5 idfmin=idfbest-4
idfmax=idfbest+5 idfmax=idfbest+4
idfstp=1 idfstp=1
ibmin=max(0,ibest-5) ibmin=max(0,ibest-5)
ibmax=min(ibest+5,NMAX/NDOWN-1) ibmax=min(ibest+5,NMAX/NDOWN-1)
@ -265,6 +265,11 @@ subroutine ft4_decode(cdatetime0,tbuf,nfa,nfb,nfqso,iwave,ndecodes,mycall, &
if(idupe.eq.1) exit if(idupe.eq.1) exit
ndecodes=ndecodes+1 ndecodes=ndecodes+1
decodes(ndecodes)=message decodes(ndecodes)=message
if(snr.gt.0.0) then
xsnr=10*log10(snr)-14.0
else
xsnr=-18.0
endif
nsnr=nint(xsnr) nsnr=nint(xsnr)
freq=f0 freq=f0
tsig=mod(tbuf + ibest/750.0,100.0) tsig=mod(tbuf + ibest/750.0,100.0)

4
lib/ft4/ft4_params.f90
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@ -11,6 +11,6 @@ parameter (NZ=NSPS*NN) !Sync and Data samples (52736)
parameter (NZ2=NSPS*NN2) !Total samples in shaped waveform (53760) parameter (NZ2=NSPS*NN2) !Total samples in shaped waveform (53760)
parameter (NMAX=5*12000) !Samples in iwave (60,000) parameter (NMAX=5*12000) !Samples in iwave (60,000)
parameter (NFFT1=2048, NH1=NFFT1/2) !Length of FFTs for symbol spectra parameter (NFFT1=2048, NH1=NFFT1/2) !Length of FFTs for symbol spectra
parameter (NSTEP=NSPS/4) !Coarse time-sync step size parameter (NSTEP=NSPS) !Coarse time-sync step size
parameter (NHSYM=NMAX/NSTEP-3) !Number of symbol spectra (1/4-sym steps) parameter (NHSYM=(NMAX-NFFT1)/NSTEP) !Number of symbol spectra (1/4-sym steps)
parameter (NDOWN=16) !Downsample factor parameter (NDOWN=16) !Downsample factor

39
lib/ft4/getcandidates4.f90
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@ -56,19 +56,32 @@ subroutine getcandidates4(id,fa,fb,syncmin,nfqso,maxcand,savg,candidate, &
ncand=0 ncand=0
f_offset = -1.5*12000/512 f_offset = -1.5*12000/512
do i=1,maxcand do i=nfa+1,nfb-1
ipk=maxloc(savsm(nfa:nfb)) if(savsm(i).ge.savsm(i-1) .and. savsm(i).ge.savsm(i+1) .and. savsm(i).ge.syncmin) then
ip=nfa-1+ipk(1) del=0.5*(savsm(i-1)-savsm(i+1))/(savsm(i-1)-2*savsm(i)+savsm(i+1))
xmax=savsm(ip) fpeak=(i+del)*df+f_offset
savsm(max(1,ip-8):min(NH1,ip+8))=0.0 speak=savsm(i) - 0.25*(savsm(i-1)-savsm(i+1))*del
if(xmax.ge.syncmin) then ncand=ncand+1
ncand=ncand+1 if(ncand.gt.maxcand) exit
candidate(1,ncand)=ip*df+f_offset candidate(1,ncand)=fpeak
candidate(2,ncand)=-99.9 candidate(2,ncand)=-99.99
candidate(3,ncand)=xmax candidate(3,ncand)=speak
else endif
exit
endif
enddo enddo
! do i=1,maxcand
! ipk=maxloc(savsm(nfa:nfb))
! ip=nfa-1+ipk(1)
! xmax=savsm(ip)
! savsm(max(1,ip-8):min(NH1,ip+8))=0.0
! if(xmax.ge.syncmin) then
! ncand=ncand+1
! candidate(1,ncand)=ip*df+f_offset
! candidate(2,ncand)=-99.9
! candidate(3,ncand)=xmax
! else
! exit
! endif
! enddo
return return
end subroutine getcandidates4 end subroutine getcandidates4